[types] Move tests to tests/ directory; implement a bunch of Display tests

types/src/object.rs

@@ -54,7 +54,7 @@ impl Obj {
 impl fmt::Display for Obj {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
-            Obj::Null => write!(f, "null"),
+            Obj::Null => write!(f, "()"),
             Obj::Ptr(obj) => write!(f, "{}", obj)
         }
     }

types/src/pair.rs

@@ -14,6 +14,10 @@ pub struct Pair {
 }
 
 impl Pair {
+    pub fn new(car: Obj, cdr: Obj) -> Pair {
+        Pair { car, cdr }
+    }
+
     pub fn empty() -> Pair {
         Pair { car: Obj::Null, cdr: Obj::Null }
     }
@@ -52,11 +56,4 @@ impl fmt::Display for Pair {
 #[cfg(test)]
 mod tests {
     use super::Pair;
-
-    #[test]
-    fn display_empty_pair() {
-        let empty = Pair::empty();
-        let disp = format!("{}", empty);
-        assert_eq!(disp, "(())");
-    }
 }

types/src/sym.rs

@@ -38,13 +38,6 @@ impl fmt::Display for Sym {
 mod tests {
     use super::Sym;
 
-    #[test]
-    fn syms_display_as_strings() {
-        let sym = Sym::with_str("abc");
-        let disp = format!("{}", sym);
-        assert_eq!(disp, "abc");
-    }
-
     #[test]
     fn syms_with_the_same_name_are_equal() {
         let a = Sym::with_str("abc");

types/tests/display.rs

@@ -0,0 +1,61 @@
+/* types/tests/display.rs
+ * Eryn Wells <eryn@erynwells.me>
+ */
+
+//! Tests of how various types implement Display.
+
+extern crate sibiltypes;
+
+use sibiltypes::{Obj, Pair, Sym};
+
+
+#[test]
+fn empty_pairs_display_correctly() {
+    let empty = Pair::empty();
+    let disp = format!("{}", empty);
+    assert_eq!(disp, "(())");
+}
+
+#[test]
+fn pair_with_only_car_is_single_element_list() {
+    let sym = Obj::new(Sym::with_str("ab"));
+    let pair = Pair::with_car(sym);
+    let disp = format!("{}", pair);
+    assert_eq!(disp, "(ab)");
+}
+
+#[test]
+fn pair_with_car_and_cdr_is_dotted_pair() {
+    let ab = Obj::new(Sym::with_str("ab"));
+    let cd = Obj::new(Sym::with_str("cd"));
+    let pair = Pair::new(ab, cd);
+    let disp = format!("{}", pair);
+    assert_eq!(disp, "(ab . cd)");
+}
+
+#[test]
+fn two_pair_list_displays_as_list() {
+    let ab = Obj::new(Sym::with_str("ab"));
+    let cd = Obj::new(Sym::with_str("cd"));
+    let pair = Pair::new(ab, Obj::new(Pair::with_car(cd)));
+    let disp = format!("{}", pair);
+    assert_eq!(disp, "(ab cd)");
+}
+
+#[test]
+fn three_element_list_with_full_second_pair() {
+    let ab = Obj::new(Sym::with_str("ab"));
+    let cd = Obj::new(Sym::with_str("cd"));
+    let ef = Obj::new(Sym::with_str("ef"));
+    let pair = Pair::new(ab, Obj::new(Pair::new(cd, ef)));
+    let disp = format!("{}", pair);
+    assert_eq!(disp, "(ab cd . ef)");
+}
+
+#[test]
+fn syms_display_as_strings() {
+    let sym = Sym::with_str("abc");
+    let disp = format!("{}", sym);
+    assert_eq!(disp, "abc");
+}
+